In vitro approaches will be developed to modify the specificity and affinity of an existing zinc finger protein, Zif268. Preliminary studies demonstrate that using the phage display approach, both the sequence specificity and affinity of this protein for DNA may be changed. This approach will be further refined to create 4 proteins which bind conserved sites in the HIV-1 genome. Proteins will be characterized with respect to affinity, sequence specificity, and ability to inhibit transcription of reporter genes and replication of laboratory and primary clinical isolates of HIV-1. The utility of known cellular uptake and nuclear targeting sequences to deliver extracellular zinc finger protein from the medium to the nucleus will be examined. Selection and screening experiments will be performed to optimize the efficiency of these sequences as well as to attempt to discover new ones. To investigate their application in a gene therapy approach, stable cell lines which express the evolved proteins will be constructed and their ability to support viral replication examined.